Tentative correlation of the Duyunian (Cambrian Series 2, Stage 4) and the Taijiangian (Cambrian Series 3, Stage 5) between South China and the Mediterranean region

摘要

The base of the Duyunian Stage can be tentatively correlated with the base of the Leonian Stage on the basis of several lines of evidence: (1) the co-occurrences of Palaeolenus in the Acadoparadoxides mureroensis Zone (lower Leonian Stage), Palaeolenus lantenoisi Zone and Palaeolenus fengyangensis Zone (upper Tsanglangpuan Stage); (2) Palaeolenus sp. from the Láncara Formation (Protolenus dimarginatus Zone) below the Leonian Stage should be grouped within the genus Shifangia Chien et Yao in Lu et al., 1974 from the Paokannia-Szechuanolenus Zone and Ushbaspis Zone just below the Duyunian Stage (P. lantenoisi Zone); (3) Protolenus (Szechuanolenus) occurs just below Cambrian Stage 4 in the Mediterranean region and in South China; (4) a regressive event just below the Stage 4 base in both regions (the Leonian Event or Evento Valdemiedes Regressive Event in the Mediterranean region; Duyunian Event or middle Tsanglangpuan Regressive Event in South China). The upper Leonian Stage may be partly equivalent to the upper Duyunian Stage as shown by the presence of Dinesus in the Eccaparadoxides asturianus Zone (upper Leonian Stage) and in the Arthricocephalus jishouensis-Changaspis plana Zone and Protoryctocephalus wuxunensis Zone (upper Duyunian Stage) of South China.